While it may seem redundant, it is not without precedent; ever heard of catfish? You wouldn't think of ordering "Southern-fried Cat" instead of catfish (if you answered yes to that question, semantics are not your only problem). And what about swordfish? "I'll have the the broiled sword, a saber salad, with a side of daggers?

In addition, from my copy of Joy of Cooking, I see food species such as blackfish, bluefish, butterfish, dogfish, monkfish, tilefish and wolf fish.

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TT

"Believe those who seek the truth.
Doubt those who find it." --Andre Gide

Perchance tuna wasn't always so well known... Probably in the murky marketing history lies the answer ?

WAG: Salmon, anchovies, sprat, herring, cod, all were commercially canned or otherwise preserved for "off-the shelf" sale since the turn of the century, and were recognizable to the primarily European communities in urban America, while poorer country folk would get sacalait, catfish, whatever at the market, fresh. When tuna was first widely distributed, people probably said huh ? and it was "marketed" as tuna [as opposed to some other] fish: accent not on variety of tuna, but on the heretofore little known variety of fish.

The 1919 OED listed tuna as a California variant on tunny (probably influenced by Mexican Spanish).

In the newer OED, the first reference is to "tuna," in quotes, describing the fish in an 1881 scientific discussion. The first reference to "tuna fish" occurs in 1919, in a book or magazine article describing low-cost, nutritious meals.

I used to think that too- until one time my boss asked if I wanted a sandwich from the new deli. Asked for Tuna fish, got a tuna steak on a sub roll with nothing but mayo. It was one of the worst sandwiches I've ever had. The "fish" may be redundant but the "salad" is not.

Lots of tuna grownin along the Reyeo Grandee river, lota crawDADS too.Probably tuna at THE La Brea Tar Pits too. But I don't think I want any tar on my steakfish samich. Just some SPICY picante sauce and some friole BEANS.You can get some at THE El Chicos on Calle del Roble Street. I have heard well spoken people regularly use the term trout fish. (These repetitive redundancies were brought to you by that obnoxious idiot mr john. sig.mr john's computer)

[Well, OK, having been told in another post to look in the dictionary, I find that the prefix, a Latin intensive, is actually [i]red-[/], coupled with the Latin undare to surge < unda wave, but that spoils all the fun.]